JP2005113012A - Active ray-curable ink composition, image-forming method using the same and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active ray-curable ink composition which exhibits excellent letter qualities, causes no color mixing and can stably record highly precise images always in various printing environments, an image-forming method using the same and inkjet recording device. <P>SOLUTION: The active ray-curable ink composition comprises photo acid-generators and photopolymerizable compounds, where at least one of the photo acid-generators is a sulfonic acid-generating agent represented by general formula (A) (wherein R is CF<SB>3</SB>- or CH<SB>3</SB>-). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an actinic ray curable ink composition that can stably reproduce a high-definition image on various recording materials even under various printing environments, an image forming method using the same, and an ink jet recording apparatus.

  In recent years, the ink jet recording system can create images easily and inexpensively, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In particular, a recording device that emits and controls fine dots, ink that has improved color reproduction gamut, durability, and emission suitability, and ink absorbability, coloring material color development, surface gloss, etc. have been dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper. The image quality improvement of today's ink jet recording system is achieved only when all of the recording apparatus, ink, and special paper are available.

  However, in an inkjet system that requires dedicated paper, the recording medium is limited, and the cost of the recording medium increases. Therefore, many attempts have been made to record on a transfer medium different from dedicated paper by an ink jet method. Specifically, a phase change ink jet method using a wax ink solid at room temperature, a solvent ink jet method using an ink mainly composed of a fast-drying organic solvent, a UV ink jet method in which crosslinking is performed by ultraviolet (UV) light after recording, etc. It is.

  Among these, the UV inkjet method has been attracting attention in recent years because it has a relatively low odor compared to the solvent-based inkjet method, and can be recorded on a recording medium having no quick drying and no ink absorption. No. 200204 and JP 2000-504778 A disclose an ultraviolet curable inkjet ink.

  However, even if these inks are used, the dot diameter after landing greatly changes depending on the type of recording material and the working environment, and it is not possible to form high-definition images on various recording materials. Is possible.

On the other hand, it is known that a triarylsulfonium salt is used as a polymerization initiator in an ultraviolet curable inkjet ink (see, for example, Patent Document 1). However, ultraviolet curable ink-jet inks using only these sulfonium salts as polymerization initiators are not affected by oxygen but have a problem of being easily affected by moisture (humidity) at the molecular level.
JP 2002-188025 A (pages 2 to 7)

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and its purpose is to have excellent character quality, no color mixing, and always stably record a high-definition image even under various printing environments. An actinic ray curable ink composition capable of forming an image, an image forming method using the same, and an ink jet recording apparatus.

The above object of the present invention is achieved by the following configurations.
(Claim 1)
In the actinic ray curable ink composition containing a photoacid generator and a photopolymerizable compound, at least one of the photoacid generators is a sulfonic acid generator represented by the following general formula (A). An actinic ray curable ink composition characterized by the above.

[Wherein, R represents CF ₃ — or CH ₃ —. ]
(Claim 2)
The actinic ray curable ink composition according to claim 1, wherein at least one of the photopolymerizable compounds is a compound having an oxetane ring.
(Claim 3)
The actinic ray curable ink composition according to claim 1, wherein at least one of the photopolymerizable compounds is a compound having an oxirane group.
(Claim 4)
The photopolymerizable compound contains 30 to 95% by mass of a compound having an oxetane ring, 5 to 70% by mass of a compound having an oxirane group, and 0 to 40% by mass of a vinyl ether compound. 4. The actinic ray curable ink composition according to any one of 3 above.
(Claim 5)
The actinic ray curable ink composition according to claim 3 or 4, wherein the compound having an oxirane group is an epoxidized fatty acid ester or an epoxidized fatty acid glyceride.
(Claim 6)
The actinic ray curable ink composition according to any one of claims 1 to 5, wherein the compound having an oxetane ring is a compound represented by the following general formula (E).

[Wherein, R _{1 to} R ₆ each represents a hydrogen atom or a substituent. However, at least one of the groups represented by R _{3 to} R ₆ is a substituent. ]
(Claim 7)
The monofunctional oxetane compound having one oxetane ring and the polyfunctional oxetane compound having two or more oxetane rings are used in combination as the photopolymerizable monomer. An actinic ray curable ink composition.
(Claim 8)
The actinic ray curable ink composition according to claim 1, wherein the viscosity at 25 ° C. is 7 to 50 mPa · s.
(Claim 9)
The actinic ray curable ink composition according to claim 1, further comprising a pigment.
(Claim 10)
An image forming method in which the actinic ray curable ink composition according to any one of claims 1 to 9 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material, An image forming method comprising irradiating an actinic ray for 0.001 to 2.0 seconds after the actinic ray curable ink composition has landed.
(Claim 11)
An image forming method in which the actinic ray curable ink composition according to any one of claims 1 to 9 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material, An image forming method, wherein the total ink film thickness after landing with an actinic ray curable ink composition and curing by irradiation with actinic rays is 2 to 20 μm.
(Claim 12)
An image forming method in which the actinic ray curable ink composition according to any one of claims 1 to 9 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material, An image forming method, wherein the amount of ink droplets ejected from each nozzle of an ink jet recording head is 2 to 15 pl.
(Claim 13)
An image forming method in which the actinic ray curable ink composition according to any one of claims 1 to 9 is jetted onto a recording material from an ink jet recording head, and printing is performed on the recording material. An image forming method comprising forming an image by ejecting the actinic ray curable ink composition from a head type ink jet recording head.
(Claim 14)
It is an inkjet recording device used for the image forming method of any one of Claims 10-13, Comprising: It discharges, after heating actinic-light curable ink composition and an inkjet recording head to 35-100 degreeC. An ink jet recording apparatus.

  According to the present invention, there is provided an actinic ray curable ink composition that has excellent character quality, does not cause color mixing, and can stably record a high-definition image at all times under various printing environments. It is possible to provide an image forming method and an ink jet recording apparatus using the above.

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  The inventor of the present invention contains a photoacid generator represented by the general formula (A) in the actinic ray curable ink composition, whereby the curability is dramatically improved and the curing environment ( For example, it has been found that good curability can be obtained regardless of temperature and humidity, and the present invention has been achieved.

  The photoacid generator represented by the general formula (A) has been used mainly in the field of photoresists and coatings, but the light of an actinic ray curable ink composition (hereinafter also simply referred to as ink). It has not been known to be effective when used as an acid generator. In particular, when used in combination with a compound containing an oxetane ring, the ejection stability, which is an important characteristic for ink jet recording, is very good, and the ink is not affected by the curing environment on the recording material. This is an epoch-making structure that can easily control the dot diameter after landing and can form a high-quality image with high reproducibility.

  In the ink of the present invention, the photopolymerizable compound preferably contains 30 to 95% by mass of a compound having an oxetane ring, 5 to 70% by mass of a compound having an oxirane group, and 0 to 40% by mass of a vinyl ether compound. Thus, the curability and the discharge stability can be further improved.

  Furthermore, it discovered that both sclerosis | hardenability and discharge stability improved markedly by using the oxetane compound represented by the said general formula (E). When only the oxetane compound is used as the photopolymerizable compound, it is more preferable to use a monofunctional oxetane compound and a polyfunctional oxetane compound having two or more oxetane rings in combination.

  Hereinafter, the present invention will be described in detail.

  First, the photoacid generator represented by the general formula (A) according to the present invention will be described.

In the general formula (A), R represents CF ₃ — and CH ₃ —, respectively. P-CH ₃ C ₆ H as _{R 4 -, n-C 3} H 7 - photoacid generator having a like (e.g., manufactured by Ciba Specialty Chemicals CGI268, CGI263) are known, these light An acid generator has a weak acid strength and insufficient curability.

  Examples of the photoacid generator represented by the general formula (A) according to the present invention include THE CHEMICAL SOCIETY OF JAPAN Voi. 71 no. 11, 1998, or the method described in Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1997, Rev. 1, pages 187 to 192). Can be synthesized.

  In the present invention, other known photoacid generators can be used together with the photoacid generator represented by the general formula (A) described above.

  As the photoacid generator that can be used in combination, for example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used. "See Bunshin Publishing (1993), pages 187-192).

  Examples of suitable compounds that can be used in combination with the photoacid generator represented by the general formula (A) of the present invention are given below.

First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, phosphonium, etc. be able to.

  Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, a sulfonated substance that generates a sulfonic acid different from the general formula (A) according to the present invention can be exemplified, and specific compounds thereof are exemplified below.

  Thirdly, halides that generate hydrogen halide can also be used, and specific compounds thereof are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

  The ink according to the present invention includes, for the first time, JP-A-8-248561 and JP-A-9-34106, and an acid proliferating agent that newly generates an acid by an acid generated by actinic ray irradiation that has already been known. It is preferable to do. By using an acid multiplication agent, it is possible to further improve discharge stability.

  The ink of the present invention preferably contains a compound having at least one oxetane ring as the photopolymerizable monomer.

  The oxetane compound that can be used in the present invention is a compound having an oxetane ring, and any known oxetane compound as disclosed in JP-A Nos. 2001-220526 and 2001-310937 can be used. .

  In the present invention, it is particularly preferable to use a compound having an oxetane ring represented by the general formula (E) for further improving curability and ejection stability.

  Hereinafter, the compound containing the oxetane ring represented by the general formula (E) according to the present invention will be described.

In the general formula (E), R _{1 to} R ₆ each represent a hydrogen atom or a substituent, and at this time, R _{3 to} R ₆ do not simultaneously represent a hydrogen atom.

  Examples of the compound having one oxetane ring in the molecule include compounds represented by the following general formulas (2) to (5).

In the above general formulas (2) to (5), each Z is independently an oxygen or sulfur atom, or a divalent hydrocarbon group that may contain an oxygen or sulfur atom in the main chain, R _{1 to} R ₆ are An alkyl group having 1 to 6 carbon atoms such as a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group or a butyl group, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, a furyl group or a thienyl group; Groups R ₇ and R ₈ are alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group or butyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group 2-methyl-2-propenyl group, 1-butenyl group, 2-butenyl group or 3-butenyl group, such as alkenyl group having 1 to 6 carbon atoms, phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group Or an aryl group such as a phenoxyethyl group, an alkylcarbonyl group having 1 to 6 carbon atoms such as a propylcarbonyl group, a butylcarbonyl group or a pentylcarbonyl group, an carbonyl group such as an ethoxycarbonyl group, a propoxycarbonyl group or a butoxycarbonyl group. Represents an alkoxycarbamoyl group having 1 to 6 carbon atoms such as ˜6 alkoxycarbonyl groups, ethoxycarbamoyl group, propylcarbamoyl group or butylpentylcarbamoyl group;

As the oxetane ring-containing compound used in the present invention, in the above general formulas (2) to (5), R ₁ is a lower alkyl group, particularly ethyl group, R ₇ and R ₈ are propyl group, butyl group, phenyl group or A benzyl group and those in which Z is a hydrocarbon group containing no oxygen or sulfur atom are preferred. Moreover, R < ₃ > -R < ₆ > does not represent a hydrogen atom simultaneously.

  Examples of the compound having two or more oxetane rings in the molecule include compounds represented by the following general formulas (6), (7), and (13).

In the above general formulas (6) and (7), m is 2, 3 or 4, Z is independent, oxygen or sulfur atom, or a divalent hydrocarbon group which may contain oxygen or sulfur atom, R ₁ is a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group or a butyl group, such as an alkyl group having 1 to 6 carbon atoms, a phenyl group, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group Or a furyl group, R ₉ is, for example, a linear or branched alkylene group having 1 to 12 carbon atoms represented by the following general formula (8), a linear or branched poly (alkyleneoxy) group,

(In the general formula (8), R ₁₀ represents a lower alkyl group such as a methyl group, an ethyl group or a propyl group.)
Or the polyvalent group selected from the group which consists of following General formula (9), (10) and (11) is represented.

In the general formula (9), n is 0 or an integer of 1 to 2000, R ₁₁ is an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, and the following general formula (12) Represents a group selected from the group consisting of

In the general formula (12), j is 0 or an integer of 1 to 100, R ₁₃ is an alkyl having 1 to 10 carbon atoms, R ₁₂ is a carbon number such as a methyl group, an ethyl group, a propyl group, or a butyl group. 1-10 alkyl groups are represented.

In the general formula (10), R ₁₄ represents a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group or the like, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a halogen atom, A nitro group, a cyano group, a mercapto group, a lower alkyl carboxylate group or a carboxyl group is represented.

In the general formula (11), R ₁₅ represents an oxygen atom, a sulfur atom, NH, SO, SO ₂ , CH ₂ , C (CH ₃ ) ₂ or C (CF ₃ ) ₂ .

As the compound having an oxetane ring used in the present invention, in the above general formulas (6) and (7), R ₁ is a lower alkyl group, particularly an ethyl group, R ₉ is represented by R ₁₄ in the general formula (10). A group that is a hydrogen atom, a hexamethylene group, in general formula (8), R ₁₀ is an ethyl group, in general formulas (9) and (12), R ₁₂ and R ₁₃ are methyl groups, and Z does not contain an oxygen or sulfur atom What is a hydrocarbon group is preferable. R _{3 to} R ₆ do not represent a hydrogen atom at the same time.

In the general formula (13), r is an integer of 25 to 200, R ₁₃ has the same meaning as R ₁₃ in the general formula (12), R ₁₆ represents an alkyl group or a trialkylsilyl group having 1 to 4 carbon atoms It is. R _{4 to} R ₆ do not represent a hydrogen atom at the same time.

  Although the specific example of a compound represented by general formula (E) below is shown, this invention is not limited only to these.

  These compounds can be easily synthesized by referring to the following documents, including the method described in the fourth lecture of "Catchball of Polymer Science and Organic Chemistry".

1) Hu Xianming, Richard M. et al. Kellogg, Synthesis, 533-538, May (1995)
2) A. O. Fitton, J .; Hill, D.C. Ejan, R.A. Miller, Synth. , 12, 1140 (1987)
3) Toshiro Imai and Shinya Nishida, Can. J. et al. Chem. Vol. 59, 2503-2509 (1981)
4) Nobujiro Shimizu, Shintaro Yamaoka, and Yuho Tsuno, Bull. Chem. Soc. Jpn. 56, 3853-3854 (1983)
5) Walter Fisher and Cyril A. Grob, Helv. Chim. Acta. , 61, 2336 (1978)
6) Chem. Ber. 101, 1850 (1968)
7) “Heterocyclic Compounds with Three-and Four-membered Rings”, Part Two, Chapter IX, Interscience Publishers, John Wiley & Sons, New York, 1964.
8) H.M. A. J. et al. Curless, “Synthetic Organic Photochemistry”, Plenum, New York (1984).
9) M.M. Braun, Nachr. Chem. Tech. Lab. 33, 213 (1985)
10) S.M. H. Schroeter, J. et al. Org. Chem. , 34, 5, 1181 (1969)
11) D. R. Arnold, Adv. Photochem. 6,301 (1968)
12) “Heterocyclic Compounds with Three-and Four-membered Rings”, Part Two, Chapter IX, Interscience Publishers, John Wiley & Sons, New York, 1964.
In the ink of the present invention, it is possible to use a monofunctional oxetane compound containing one oxetane ring and a polyfunctional oxetane compound containing two or more oxetane rings in combination with the film strength after curing and the recording material. It is further preferable in improving the adhesion. However, if a compound having 5 or more oxetane rings is used, the viscosity of the ink composition becomes high, which makes it difficult to handle, and the glass transition temperature of the ink composition becomes high. Sex is not enough. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.

  In the ink of the present invention, it is possible to use a monofunctional oxetane compound containing one oxetane ring and a polyfunctional oxetane compound containing two or more oxetane rings in combination with the film strength after curing and the recording material. It is further preferable in improving the adhesion. However, if a compound having 5 or more oxetane rings is used, the viscosity of the ink composition becomes high, which makes it difficult to handle and increases the glass transition temperature of the ink composition. Sex is not enough. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.

  In the present invention, it is preferable to contain a compound having at least one oxirane group in order to further improve the curability and ejection stability.

  The compound having an oxirane ring according to the present invention is a compound having one or more oxirane rings in the molecule, and any of monomers, oligomers or polymers that are usually used as an epoxy resin can be used.

  Specific examples include conventionally known aromatic epoxides, alicyclic epoxides, and aliphatic epoxides. Hereinafter, the epoxide means a monomer or an oligomer thereof. These compounds may be used alone or in combination of two or more as required.

  Examples of the epoxy compound include the following aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  A preferable aromatic epoxide is a di- or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin, such as bisphenol A or an alkylene oxide thereof. Examples thereof include di- or polyglycidyl ethers of adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or its alkylene oxide adducts, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is preferable.

  Preferred aliphatic epoxides include di- or polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or Diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, polyethylene glycol or its alkylene oxide adduct Diglycidyl ethers of polyalkylene glycols such as diglycidyl ethers, polypropylene glycols or diglycidyl ethers of adducts thereof Tel and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in view of fast curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable. In the present invention, one of the epoxides may be used alone, or two or more may be used in appropriate combination.

  The ink of the present invention preferably contains an epoxidized fatty acid ester or an epoxidized fatty acid glyceride as an epoxy compound having an oxirane group from the viewpoint of safety such as AMES and sensitization.

  The epoxidized fatty acid ester and the epoxidized fatty acid glyceride are not particularly limited as long as an epoxy group is introduced into the fatty acid ester or fatty acid glyceride.

  The epoxidized fatty acid ester is produced by epoxidizing an oleic acid ester, and examples thereof include methyl epoxy stearate, butyl epoxy stearate, octyl epoxy stearate and the like. Similarly, the epoxidized fatty acid glyceride is produced by epoxidizing soybean oil, linseed oil, castor oil and the like, and epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil and the like are used.

  Furthermore, in the present invention, any known vinyl ether compound may be used.

  Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylol. Di- or trivinyl ether compounds such as propane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n-pro Vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in appropriate combination.

  In the present invention, the ink preferably contains 30 to 95% by mass of a compound having an oxetane ring, 5 to 70% by mass of a compound having an oxirane group, and 0 to 40% by mass of a vinyl ether compound as a photopolymerizable compound. With this configuration, both curability and ejection stability are improved.

  The ink of the present invention contains various known dyes or pigments together with the above-mentioned actinic ray curable compositions, but preferably contains pigments.

  The pigments that can be preferably used in the present invention are listed below, but the present invention is not limited thereto.

C. I Pigment Yellow-1, 3, 12, 13, 14, 17, 81, 83, 87, 95, 109, 42,
C. I Pigment Orange-16, 36, 38,
C. I Pigment Red-5, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 144, 146, 185, 101,
C. I Pigment Violet-19, 23,
C. I Pigment Blue-15: 1, 15: 3, 15: 4, 18, 60, 27, 29,
C. I Pigment Green-7, 36,
C. I Pigment White-6, 18, 21,
C. I Pigment Black-7,
In the present invention, it is preferable to use white ink for the purpose of enhancing the color concealment property on a transparent substrate such as a plastic film. In particular, in soft packaging printing and label printing, it is preferable to use white ink, but since the discharge amount increases, there is a limit to the amount of use from the viewpoint of discharge stability and the occurrence of curling and wrinkling of the recording material. is there.

  For the dispersion of the pigment, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used. Further, a dispersing agent can be added when dispersing the pigment. As the dispersant, a polymer dispersant is preferably used, and examples of the polymer dispersant include Avecia's Solsperse series and Ajinomoto Fine-Techno's PB series. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is used using a solvent or a polymerizable compound. However, the radiation curable ink used in the present invention is preferably solvent-free because it reacts and cures immediately after ink landing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The pigment is preferably dispersed so that the average particle diameter of the pigment particles is 0.08 to 0.5 μm, and the maximum particle diameter is 0.3 to 10 μm, preferably 0.3 to 3 μm. The selection of the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  In the ink of the present invention, the color material concentration is preferably 1 to 10% by mass of the whole ink.

  Various additives other than those described above can be used in the actinic ray curable ink of the present invention. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added. In addition, for the purpose of improving storage stability, any known basic compound can be used, but representative examples include basic organic compounds such as basic alkali metal compounds, basic alkaline earth metal compounds, and amines. Compounds and the like. It is also possible to combine a radically polymerizable monomer and an initiator into a radical / cation hybrid type curable ink.

  In the ink of the present invention, it is preferable that the viscosity at 25 ° C. is 7 to 50 mPa · s in order to obtain stable discharge and good curability regardless of the curing environment (temperature / humidity).

  As a recording material that can be used in the present invention, in addition to ordinary uncoated paper, coated paper, etc., various non-absorbable plastics and films used for so-called soft packaging can be used. For example, polyethylene terephthalate (PET) film, stretched polystyrene (OPS) film, stretched polypropylene (OPP) film, stretched nylon (ONy) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, triacetyl cellulose (TAC) ) A film can be mentioned. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, PVA, rubbers and the like can be used. Moreover, it is applicable also to metals and glass.

  The surface energy of these various plastic films varies greatly depending on the characteristics of the material, and it has conventionally been a problem that the dot diameter after ink landing varies depending on the recording material. With the configuration of the present invention, a good high-definition image can be formed on a wide range of recording materials having a surface energy of 35 to 60 mN / m, including OPP films having a low surface energy, OPS films, and PET having a relatively large surface energy. .

  In the present invention, it is more advantageous to use a long (web) recording material in terms of the cost of the recording material such as packaging cost and production cost, the production efficiency of the print, and the ability to cope with printing of various sizes. is there.

  Next, the image forming method of the present invention will be described.

  In the image forming method of the present invention, a method is preferred in which the ink is ejected and drawn on a recording material by an ink jet recording method, and then the ink is cured by irradiation with an actinic ray such as ultraviolet rays.

(Total ink film thickness after ink landing)
In the present invention, the total ink film thickness after the ink has landed on the recording material and cured by irradiation with actinic rays is preferably 2 to 20 μm. In the actinic ray curable inkjet recording in the screen printing field, the total ink film thickness currently exceeds 20 μm, but in the flexible packaging printing field where the recording material is often a thin plastic material, the recording material described above is used. In addition to the problem of curling and wrinkles, there is a problem in that the entire printed material is changed in its strain and texture.

  Here, “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the recording material, and even for a single color, other two colors are superimposed (secondary color), three colors are superimposed, four colors are used. Even when recording is performed by the overlapping (white ink base) inkjet recording method, the meaning of the total ink film thickness is the same.

(Ink ejection conditions)
As the ink ejection conditions, it is preferable from the viewpoint of ejection stability that the recording head and ink are heated to 35 to 100 ° C. and ejected. Actinic radiation curable ink has a large viscosity fluctuation range due to temperature fluctuations, and the viscosity fluctuations directly affect the droplet size and droplet ejection speed, causing image quality degradation. It is necessary to keep. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  Moreover, in this invention, it is preferable that the amount of droplets discharged from each nozzle is 2 to 15 pl. Originally, in order to form a high-definition image, it is necessary for the amount of droplets to be within this range, but when discharging with this amount of droplets, the above-described discharge stability becomes particularly severe. According to the present invention, even when ejection is performed with a small droplet amount such as 2 to 15 pl, the ejection stability is improved and a high-definition image can be stably formed.

(Light irradiation conditions after ink landing)
In the image forming method of the present invention, the active light is preferably irradiated for 0.001 second to 2.0 seconds after landing of the ink, more preferably 0.001 second to 1 as the active light irradiation condition. 0.0 seconds, more preferably 0.001 to 0.5 seconds. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

  As a method for irradiating actinic rays, the basic method is disclosed in JP-A-60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side of the head unit and irradiating the recording unit with UV light is disclosed. Yes. Any of these irradiation methods can be used in the image forming method of the present invention.

  In addition, irradiation with actinic rays is divided into two stages. First, actinic rays are irradiated by the above-described method within 0.001 to 2.0 seconds after ink landing, and further, actinic rays are irradiated after all printing is completed. The method is also a preferred embodiment. By dividing the irradiation of actinic rays into two stages, it is possible to further suppress the shrinkage of the recording material that occurs during ink curing.

  Conventionally, in the UV ink jet system, a light source with high illuminance in which the total power consumption of the light source exceeds 1 kW · hr is usually used in order to suppress dot spreading and bleeding after ink landing. However, when these light sources are used, particularly in printing on a shrink label or the like, the shrinkage of the recording material is so large that it cannot be used practically.

  In the present invention, it is preferable to use an actinic ray having a maximum illuminance in a wavelength region of 254 nm, and a high-definition image can be formed even when a light source having a total power consumption of 1 kW · hr or more is used, and the recording material is contracted. Is also within a practically acceptable level.

  In the present invention, it is preferable that the total power consumption of the light source for irradiating actinic rays is less than 1 kW · hr. Examples of the light source having a total power consumption of less than 1 kW · hr include, but are not limited to, a fluorescent tube, a cold cathode tube, a hot cathode tube, and an LED.

  Next, an ink jet recording apparatus (hereinafter simply referred to as a recording apparatus) of the present invention will be described.

  The recording apparatus of the present invention will be described below with reference to the drawings as appropriate. Note that the recording apparatus of the drawings is merely one aspect of the recording apparatus of the present invention, and the recording apparatus of the present invention is not limited to this drawing.

  FIG. 1 is a front view showing the configuration of the main part of the recording apparatus of the present invention. The recording apparatus 1 includes a head carriage 2, a recording head 3, an irradiation unit 4, a platen unit 5, and the like. In the recording apparatus 1, the platen unit 5 is installed under the recording material P. The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the recording material P. As a result, a high-definition image can be reproduced very stably.

  The recording material P is guided by the guide member 6 and moves from the near side to the far side in FIG. 1 by the operation of the conveying means (not shown). A head scanning unit (not shown) scans the recording head 3 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction in FIG.

  The head carriage 2 is installed on the upper side of the recording material P, and stores a plurality of recording heads 3 to be described later according to the number of colors used for image printing on the recording material P, with the discharge ports arranged on the lower side. The head carriage 2 is installed with respect to the main body of the recording apparatus 1 in such a manner that it can reciprocate in the Y direction in FIG. 1, and reciprocates in the Y direction in FIG. 1 by driving the head scanning means.

  In FIG. 1, the head carriage 2 is white (W), yellow (Y), magenta (M), cyan (C), black (K), light yellow (Ly), light magenta (Lm), and light cyan (Lc). Although the drawing is carried out assuming that the recording heads 3 of light black (Lk) and white (W) are accommodated, the number of colors of the recording heads 3 accommodated in the head carriage 2 is determined as appropriate. Is.

  The recording head 3 has a discharge port by operating a discharge means (not shown) provided with a plurality of actinic ray curable inks (for example, UV curable ink) supplied by an ink supply means (not shown). To the recording material P. The UV ink ejected by the recording head 3 is composed of a coloring material, a polymerizable monomer, an initiator, and the like, and the monomer crosslinks when the initiator acts as a catalyst when irradiated with ultraviolet rays. It has the property of being cured by a polymerization reaction.

  During the scanning in which the recording head 3 moves from one end of the recording material P to the other end of the recording material P in the Y direction in FIG. 1 by driving the head scanning means, a certain area (landing possible area) in the recording material P On the other hand, UV ink is ejected as ink droplets, and ink droplets are landed on the landable area.

  The above scanning is performed as many times as necessary, and after UV ink is ejected toward one landable area, the recording material P is appropriately moved from the front to the back in FIG. 1, the recording head 3 discharges UV ink to the next landable area adjacent in the depth direction in FIG.

  By repeating the above operation and ejecting the UV ink from the recording head 3 in conjunction with the head scanning means and the conveying means, an image composed of an aggregate of UV ink droplets is formed on the recording material P.

  The irradiation unit 4 includes an ultraviolet lamp that emits ultraviolet light in a specific wavelength region with stable exposure energy and a filter that transmits ultraviolet light of a specific wavelength. Here, as the ultraviolet lamp, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a cold cathode tube, a hot cathode tube, a black light, an LED (light emitting diode) and the like can be applied. A cathode tube, a hot cathode tube, a mercury lamp or black light is preferred. In particular, a low-pressure mercury lamp, a hot cathode tube, a cold cathode tube, and a germicidal lamp that emit ultraviolet light having a wavelength of 254 nm are preferable because they can prevent bleeding and control the dot diameter efficiently. By using black light as the radiation source of the irradiation means 4, the irradiation means 4 for curing the UV ink can be produced at low cost.

  The irradiating means 4 has substantially the same shape as the maximum one that can be set by the recording apparatus (UV inkjet printer) 1 among the landable areas in which the recording head 3 ejects UV ink by one scan driven by the head scanning means. , Having a shape larger than the landable area.

  The irradiation means 4 is fixed on both sides of the head carriage 2 so as to be substantially parallel to the recording material P.

  As described above, as a means for adjusting the illuminance of the ink discharge portion, not only the entire recording head 3 is shielded, but in addition, when the distance between the irradiation means 4 and the recording material P is h1, the recording head 3 is used. It is effective to increase the distance (h2) between the ink discharge section 31 and the recording material P (h1 <h2), or to increase the distance (d) between the recording head 3 and the irradiation means 4 (d is increased). It is. Further, it is more preferable to provide a bellows structure 7 between the recording head 3 and the irradiation means 4.

  Here, the wavelength of the ultraviolet rays irradiated by the irradiation means 4 can be changed as appropriate by replacing the ultraviolet lamp or filter provided in the irradiation means 4.

  The ink of the present invention has excellent ejection stability and is particularly effective when an image is formed using a line head type recording apparatus.

  FIG. 2 is a top view illustrating another example of the configuration of the main part of the ink jet recording apparatus.

  The ink jet recording apparatus shown in FIG. 2 is called a line head system, and a plurality of ink jet recording heads 3 of each color are fixedly arranged on the head carriage 2 so as to cover the entire width of the recording material P. ing.

  On the other hand, on the downstream side of the head carriage 2, there is provided irradiation means 4 arranged so as to cover the entire width of the recording material P and cover the entire area of the ink printing surface. As the ultraviolet lamp used in the illuminating means 4, the same one as described in FIG. 1 can be used.

  In this line head system, the head carriage 2 and the irradiating means 4 are fixed, and only the recording material P is conveyed, and ink ejection and curing are performed to form an image.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Preparation of ink composition set>
Ink composition sets 1 to 6 having the compositions shown in Tables 1 to 6 were prepared according to the following method.

  5 parts by mass of a dispersant (PB822 manufactured by Ajinomoto Fine-Techno Co., Ltd.) and each photopolymerizable compound described in Tables 1 to 6 were placed in a stainless beaker and stirred for 1 hour while heating on a 65 ° C hot plate. Mix and dissolve. Next, after adding the coloring materials described in Tables 1 to 6 to this solution, the solution was placed in a plastic bottle together with 200 g of zirconia beads having a diameter of 1 mm and sealed, and subjected to dispersion treatment for 2 hours using a paint shaker. Next, the zirconia beads are removed, and various additives such as photoacid generators, sensitizers, compatibilizers, basic compounds, and surfactants are added in the combinations shown in Tables 1 to 6, which are clogged with the printer. For prevention, ink composition sets 1 to 6 were prepared by filtration through a 0.8 μm membrane filter.

  The ink viscosity of each color of each ink composition set prepared above is as follows. The viscosity was expressed as the viscosity width at the maximum and minimum viscosity of each color ink at 25 ° C.

Ink composition set 1: 16 to 19 mPa · s
Ink composition set 2: 23 to 26 mPa · s
Ink composition set 3: 30 to 34 mPa · s
Ink composition set 4: 28 to 32 mPa · s
Ink composition set 5:30 to 33 mPa · s
Ink composition set 6: 28 to 33 mPa · s

  Details of each ink, each compound, and display described in Tables 1 to 6 are as follows.

K: Dark black ink C: Dark cyan ink M: Dark magenta ink Y: Dark yellow ink W: White ink Lk: Light black ink Lc: Light cyan ink Lm: Light magenta ink Ly: Light yellow ink Color material 1: C.I. I. pigment Black 7
Color material 2: C.I. I. pigment Blue 15: 3
Color material 3: C.I. I. pigment Red 57: 1
Color material 4: C.I. I. pigment Yellow 13
Coloring material 5: Titanium oxide (anatase type average particle size 0.20 μm)
[Photopolymerizable compound]
<* E1: Alicyclic epoxy compound>
Celoxide 3000: manufactured by Daicel Chemical Industries, Ltd. Celoxide 2021P: manufactured by Daicel Chemical Industries, Ltd. <* E2: Epoxidized linseed oil>
Vf9040: Vikoflex 9040 (manufactured by ATOFINA)
<* E3: Epoxidized soybean oil>
Vf7010: Vikoflex 7010 (manufactured by ATOFINA)
<* O: Oxetane compound>
OXT-101: Toagosei Co., Ltd. OXT-221: Toagosei Co., Ltd. [Photoacid generator]
I-250: Irgacure 250 Ciba Specialty Chemicals UVI6992: Dow Chemical Propion Carbonate 50% solution [Sensitizer]
CS-7102: Nippon Soda Co., Ltd. [Surfactant]
F178k: Megafax F178k Perfluoroalkyl group-containing acrylic oligomer (Dainippon Ink Chemical Co., Ltd.)
F1405: Megafax F1405 Perfluoroalkyl group-containing ethylene oxide adduct (manufactured by Dainippon Ink & Chemicals, Inc.)
F475: Megafax F475 Perfluoroalkyl group-containing acrylic oligomer (Dainippon Ink & Chemicals, Inc.)
[Compatibilizer]
Alastar 700: Styrene / maleic resin Arakawa Chemical Co., Ltd. R100: Haritac R100 (Rosin-modified maleic resin, Harima Chemical Co., Ltd.)
145P: Halitack 145P (Rosin-modified maleic resin, Harima Chemical Co., Ltd.)
[Dispersant]
PB822: Ajinomoto Fine Techno Co., Ltd. [Others]
* 1: N-ethyldiethanolamine (basic compound)
* 2: Tributylamine (basic compound)
* 3: Propylene carbonate (reagent, manufactured by Kanto Chemical Co., Inc.)
<< Inkjet image forming method >>
Each ink composition set 1 to 3 prepared above is loaded into an ink jet recording apparatus having the structure shown in FIG. 1 equipped with a piezo type ink jet nozzle, and has a width of 600 mm and a length having each surface energy shown in Table 7. The following image recording was continuously performed on each long recording material of 500 m. The ink supply system was composed of an ink tank, a supply pipe, a front chamber ink tank immediately before the head, a pipe with a filter, and a piezo head. The ink was insulated from the front chamber tank to the head portion and heated at 50 ° C. The piezo head was driven so that 2 to 15 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi, and each ink was ejected continuously. After each ink landed, the ink was cured by irradiating with ultraviolet rays from each irradiation light source shown in Table 7 instantly (less than 0.5 seconds after landing) by the lamp units on both sides of the carriage. When the total ink film thickness was measured after image recording, it was in the range of 2.3 to 13 μm. In the present invention, dpi represents the number of dots per 2.54 cm.

  Next, each image was formed in the same manner using the ink composition sets 4 to 6 using the line head type ink jet recording apparatus shown in FIG.

  Printing was performed by the above two methods under three conditions: an environment of 10 ° C. and 20% RH, an environment of 25 ° C. and 50% RH, and an environment of 30 ° C. and 80% RH.

  In addition, the detail of each irradiation light source of Table 7 is as follows.

Irradiation light source A: High pressure mercury lamp VZero085 (manufactured by INTEGRATION TECHNOLOGY)
Irradiation light source B: Metal halide lamp (manufactured by Nippon Battery Co., Ltd. MAL400NL power = 3 kW · hr 120 W / cm)
Moreover, the illumination intensity of each irradiation light source of Table 7 measured and displayed the integrated illumination intensity of 254 nm using UVPF-A1 by Iwasaki Electric Co., Ltd.

  Details of the abbreviations of the recording materials shown in Table 7 are as follows.

OPP: oriented polypropylene
PET: Polyethylene terephthalate
PVC: polyvinyl chioride

<Evaluation of inkjet recording image>
Each image recorded by the above image forming method was subjected to the following evaluations.

[Evaluation of character quality]
Using each color ink of Y, M, C, and K, a 6-point MS Mincho character was printed at a target density, and the character roughness was enlarged and evaluated with a loupe, and character quality was evaluated according to the following criteria.

◎: No rusting ○: Slight rustling is visible △: Gashesiness is visible, but it can be recognized as characters, and can be used at the last minute ×: Levels that are harsh and characters are faint and cannot be used [Evaluation of color mixing (bleeding)]
At 720 dpi, printing is performed so that each dot of Y, M, C, and K is adjacent to each other, each adjacent dot is enlarged with a loupe, the degree of bleeding is visually observed, and color mixing is evaluated according to the following criteria. .

◎: Adjacent dot shape maintains a perfect circle and no bleeding occurs. ○: Adjacent dot shape maintains an almost perfect circle and almost no bleeding occurs. Δ: Adjacent dot is slightly blurred and dot shape is slightly. Although it is broken, the level that can be used at the end ×: the level where the adjacent dots are blurred and mixed and cannot be used Table 8 shows each evaluation result obtained above.

  As is apparent from Table 8, by using the actinic ray curable composition having the constitution according to the present invention, the character quality is excellent with respect to any recording material even in various printing environments as compared with the comparative example. It can be seen that it is possible to record a high-definition image with no color mixing (bleeding, wrinkles).

It is a front view which shows an example of a structure of the principal part of the inkjet recording device of this invention. It is a top view which shows another example of a structure of the principal part of the inkjet recording device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Head carriage 3 Inkjet recording head 31 Ink ejection port 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure P Recording material

Claims (14)

In the actinic ray curable ink composition containing a photoacid generator and a photopolymerizable compound, at least one of the photoacid generators is a sulfonic acid generator represented by the following general formula (A). An actinic ray curable ink composition characterized by the above.

[Wherein, R represents CF ₃ — or CH ₃ —. ] The actinic ray curable ink composition according to claim 1, wherein at least one of the photopolymerizable compounds is a compound having an oxetane ring. The actinic ray curable ink composition according to claim 1, wherein at least one of the photopolymerizable compounds is a compound having an oxirane group. The photopolymerizable compound contains 30 to 95% by mass of a compound having an oxetane ring, 5 to 70% by mass of a compound having an oxirane group, and 0 to 40% by mass of a vinyl ether compound. 4. The actinic ray curable ink composition according to any one of 3 above. The actinic ray curable ink composition according to claim 3 or 4, wherein the compound having an oxirane group is an epoxidized fatty acid ester or an epoxidized fatty acid glyceride. The actinic ray curable ink composition according to any one of claims 1 to 5, wherein the compound having an oxetane ring is a compound represented by the following general formula (E).

[Wherein, R _{1 to} R ₆ each represents a hydrogen atom or a substituent. However, at least one of the groups represented by R _{3 to} R ₆ is a substituent. ] The monofunctional oxetane compound having one oxetane ring and the polyfunctional oxetane compound having two or more oxetane rings are used in combination as the photopolymerizable monomer. An actinic ray curable ink composition. The actinic ray curable ink composition according to claim 1, wherein the viscosity at 25 ° C. is 7 to 50 mPa · s. The actinic ray curable ink composition according to claim 1, further comprising a pigment. An image forming method in which the actinic ray curable ink composition according to any one of claims 1 to 9 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material, An image forming method comprising irradiating an actinic ray for 0.001 to 2.0 seconds after the actinic ray curable ink composition has landed. An image forming method in which the actinic ray curable ink composition according to any one of claims 1 to 9 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material, An image forming method, wherein the total ink film thickness after the actinic ray curable ink composition is landed and cured by irradiation with actinic rays is 2 to 20 μm. An image forming method in which the actinic ray curable ink composition according to any one of claims 1 to 9 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material, An image forming method, wherein the amount of ink droplets ejected from each nozzle of an ink jet recording head is 2 to 15 pl. An image forming method in which the actinic ray curable ink composition according to any one of claims 1 to 9 is jetted onto a recording material from an ink jet recording head, and printing is performed on the recording material. An image forming method comprising forming an image by ejecting the actinic ray curable ink composition from a head type ink jet recording head. It is an inkjet recording device used for the image forming method of any one of Claims 10-13, Comprising: It discharges, after heating actinic-light curable ink composition and an inkjet recording head to 35-100 degreeC. An ink jet recording apparatus.

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